introduction to pump curves - yahoo...measured over a period of time expressed in gallons per minute...
TRANSCRIPT
PAGE 2
Pump CurvesGoulds Water Technology
A performance curve is normally a curved line drawn on a grid or graph of vertical and horizontal lines. This curved line represents the performance of a specific pump. The vertical and horizontal lines represent units of measure that illustrate that performance.
In our application there is a tank or well full of water. We want to use the water for a specific process or in a home. Often the water is at a lower level and grav-ity will not allow it to flow uphill, so a pump is used. A pump is a machine used to transfer or move a volume of water (or fluid) a given distance. This volume is measured over a period of time expressed in gallons per minute (gpm) or gallons per hour (gph). This vol-ume is also referred to as capacity or flow.
Introduction to Pump Curves
The pump develops energy called discharge pressure or total dynamic head (tdh). This pressure is expressed in units of measure called pounds per square inch (psi) or feet of head(ft.). NOTE: 1 psi will push a col-umn of water up a pipe a distance of 2.31’. A perfor-mance curve is used to determine which pump best meets the system requirements.
PAGE 3
Pump CurvesGoulds Water Technology
Example 1
The graph below would be used to illustrate a pump’s performance. It is important to determine the value of each grid line or square. On the left hand side of the graph Total Dynamic Head (TDH) is shown with the unit of measure in feet. The numbers start at the bottom, left hand corner with 0 and go up the verti-cal axis. This is the ability of the pump to produce pressure expressed in feet of head, which is a term used by many engineers. Sometimes the measure will say total dynamic head -- feet of water. This is another term which means a gauge was installed at the discharge of the pump and a reading was taken in psi. This reading is converted to feet (1 psi = 2.31 feet) and water was the liquid being pumped.
0 GPM
0
010
0
m3/h
20
METERS FEET
TOTA
L D
YN
AM
IC H
EA
D
CAPACITY
100
5
200
300
400
500
15 20 25 30 35
40
60
80
100
120
140
1 2 3 4 5 6 7 8
The other unit of measure is gallons per minute and is shown across the bottom (horizontal axis). Start at the bottom, left corner with 0 and go to the right. These numbers relate to the ability of the pump to produce flow of water expressed as capacity in gallons per minute (GPM).
Also shown are the metric measures in meters for the TDH and cubic meters per hour for the capacity.
PAGE 4
Pump CurvesGoulds Water Technology
To produce a performance curve the pump is oper-ated using a pressure gauge, throttling valve and flow meter installed in the discharge pipe. The pump is run with the throttling valve completely closed so there is no flow and a reading is taken from the pressure gauge. This is referred to as the maximum shutoff pressure. Covert this psi reading (1 psi = 2.31 ft.) to feet of head and this is the pump’s maximum Total
0 GPM
0
010
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m3/h
20
METERS FEET
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CAPACITY
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15 20 25 30 35
40
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100
120
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1 2 3 4 5 6 7 8
12
Example 2a
Dynamic Head (TDH) at 0 capacity. A mark is placed on the graph to indicate this performance (Point 1). The valve is opened until the flow meter reads 5 gpm and another pressure reading is taken from the gauge. A second point (2) is marked on the graph to indicate this performance. This process is continued at 5 gpm increments across the graph.
PAGE 5
Pump CurvesGoulds Water Technology
We now connect all the points. This curved line is called a head/capacity curve. Head (H) is expressed in feet and capacity (Q) is expressed in gallons per minute (GPM). The pump will always run somewhere on the curve.
0 GPM
0
010
0
m3/h
20
METERS FEET
TOTA
L D
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CAPACITY
100
5
200
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400
500
15 20 25 30 35
40
60
80
100
120
140
1 2 3 4 5 6 7 8
H - Q
Example 2b
PAGE 6
Pump CurvesGoulds Water Technology
There are many different type curves shown in our catalog. Here is a composite performance curve (more than one pump) for the 18GS performance submers-ible. There is a separate curve for each horsepower size.
Example 3
Let’s compare two sizes:
1. First look at the 18GS07, 3/4 HP, 6 impellers. At 15 GPM capacity this model will make 158 feet.
2. Now look at the 18GS20, 2 HP, 14 impellers. At 15 GPM capacity this model will make 360 feet.
When you add impellers, the pump makes more pres-sure (expressed in feet). This allows the pump to go deeper in a well, but also takes more horsepower.
COMPOSITE PERFORMANCE CURVES
6543210
00 5 10 15 20 25
100
30 35 40
200
300
400
500
600
700
1000
0
20
60
80
100
120
140
180
200
320
CAPACITY
TOTA
L D
YN
AM
IC H
EAD
METERS
GPM
m3/h
RPM 345060 Hz
FEET
800
900
300
280
260
240
220
160
40
8
18GS50
18GS30
18GS20
18GS15
18GS10
18GS07
7
RECOMMENDED RANGE6 – 28 GPM
20Ft .
1GPM
PAGE 7
Pump CurvesGoulds Water Technology
Here is a different kind of curve you will find used on some grids called “efficiency curve”. Efficiency as a percentage is shown on the scale at the right side of the grid.
1. Find 425 GPM at 500’. From this point read vertically UP until you touch the efficiency curve line. Then go horizontally to the right to find the percent. In this example it would be 72%.
2. Find 425 GPM at 800’. From this point read vertically DOWN until you touch the efficiency curve line. Then go horizontally to the right to find the per-cent. In this example it would be 72%.
0 GPM
0
00
m3/h
METERS FEET
TOTA
L D
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AM
IC H
EA
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CAPACITY
50200
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500
20 40 60 80 10 12 14
605040302010
600
700
800
100
150
200
250
100
0
20
30
10
40
50
60
70
80
Eff
icie
ncy
— %
2
1
72%
Example 4
The highest point of the efficiency curve line is called the “B.E.P.” or “Best Efficiency Point”.
Pump manufacturers describe pumps in terms of the flow rate at the best efficiency point. In Example 4, the pump would be classified as a 425 gallon per minute pump.
We have included a sheet called (4A) “How to figure horsepower and operating cost”. You may want to make copies and pass this out. This sheet shows why, with larger pumps, you want to select the one that has the best efficiency.
EFFICIENCY CURVE LINE SHOWN BY ITSELF
PAGE 8
Pump CurvesGoulds Water Technology
BHP = Brake Horsepower 3960 = ConstantSp. Gravity = Specific Gravity of Water is (1) WATTS = Volts x Amps1 HP = 746 Watts
Note: No motor is 100% efficient, so we say 1 HP = 1000 Watts which is (1) kilowatt or KW
The formula for figuring brake horsepower (BHP) is as follows:
GPM x Total Dynamic Head (TDH) x Sp. Gravity
3960 x Efficiency (Decimal)
Select a submersible pump for the following application: 100 GPM at 375 ft. TDH 460V
There are several which will meet this application: Pump 1 65% eff. 15 HP motor (14.8 HP) Pump 2 67% eff. 15 HP motor (16.4 HP) Pump 3 67% eff. 15 HP motor (14.1 HP) Pump 4 74% eff. 15 HP motor (12.8 HP) Note: Impeller trim to 375’ TDH
Pump 1 = 14.8 HP Pump 4 Cost = $4,600 Pump 4 = 12.8 HP Pump 1 Cost = 4,280 Difference = 2.0 HP Cost difference = $ 320
We assume — 1 kilowatt hour (KWH) cost $ .10/KWH. We multiply the HP difference 2.0 HP x $ .10 and the Cost Savings per hour $ .20. If the pump runs 10 hours per day then the cost savings is $2.00 per day. In 30 days, the savings is $60. Take the cost difference and divide by the cost savings per day ($320 / $2.00) and the difference in price is paid back in 160 days.
How to Figure Horsepower and Operating Cost
PAGE 9
Pump CurvesGoulds Water Technology
Find the point 350 GPM at 300 feet. What is the ef-ficiency? 70% is correct. When your capacity/head that you plan to use falls between two horsepower sizes, the curve line you always use is the one above or the larger horsepower.
We have decided to use the 40 HP pump and our head requirements are 300 feet. We have to install a throttling valve, and throttle the pump capacity to 350 GPM. If we don’t, the pump will run with a capacity of 420 GPM.
To determine this find 350 GPM at 300’ again. From this point go horizontally to the right until you touch the 40 HP, H-Q curve line. A pump will always run somewhere on its curve. At 420 GPM what is the pump’s efficiency? 72%.
0 GPM
0
00
m3/h
METERS FEET
TOTA
L D
YN
AM
IC H
EA
D
CAPACITY
50200
300
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20 40 60 80 100 120 140
600500400300200100
600
700
800
100
150
200
250
100
0
20
30
10
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50
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70
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Eff
icie
ncy
— %
70%
50 HP/5 STG.
40 HP/4 STG.
30 HP/3 STG.
20 HP/2 STG.
10 HP/1 STG.
COMPOSITE PERFORMANCE CURVES
Example 5
There is one other consideration called upthrust, which may occur when running the pump at open discharge. Note that each curve line stops just past 575 GPM. Under normal conditions the thrust in a submersible pump is downwards, toward the motor. At abnormally high flows, which results when there is insufficient head on the pump, this thrust is upset and goes the opposite way because the impeller is not developing sufficient head. This is called upthrust. To prevent this, install a throttling valve and throttle the pump to 575 GPM when running the pump open discharge.
PAGE 10
Pump CurvesGoulds Water Technology
Here is a curve that shows Head/Capacity and also shows suction lift.
The upper left part of the curve is divided into two parts. Find 4 GPM and read vertically up. If your suc-tion lift is 20’ or 25’ the pump will make 114 feet of head. If your suction lift is 5’, 10’ or 15’, the pump will make a little more — 119 feet.
We always show what the pump will do at all points on the curve. We would not recommend or select this pump to run below 16 gallons per minute.
The vertical curve lines on the right also relate to suction lift in 5’ increments. Find 45 GPM at 70’. This
Example 6
pump will work if your suction lift is 22’ or less. Re-member as your capacity increases, your suction lift ability decreases.
When considering capacity, in gallons per minute, and the suction lift you are trying to overcome, you must stay to the left of the vertical suction curve line.
Find 45 GPM at 70’ again. If you had a 20’ lift to over-come, this pump would work fine.
Find 50 GPM at 70’. If you had a 20’ lift to overcome, this pump will not work. You are to the right of the 20’ suction curve line. The next higher horsepower model may be the pump to meet this requirement.
0 GPM
0
00
m3/h
METERS FEET
TOTA
L D
YN
AM
IC H
EA
D
CAPACITY
5
2 4 6 8 10 12 14
1284
16
16 20 2824 32 36 40 44 48 52 56 60 64 68
10
15
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30
35
10
20
30
40
50
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70
80
90
100
110
120
25’ 20’ 15’ 10’ 5’
H - Q
5’, 10’, 15’
20’, 25’
PAGE 11
Pump CurvesGoulds Water Technology
Here is a new curve line shown called BHP (Brake Horsepower). BHP is charted to the right just past ef-ficiency scale.
Find 110 GPM at 71’. From this point read vertically down until you touch the BHP curve line. Then go hori-zontally to the right to find the horsepower required.
0 GPM
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020
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m3/h
5
METERS FEET
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EA
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CAPACITY
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5 10 15 20 25 30
40 60 80 100 120 140
20
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1
2
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43.1
EFF. BHP %
EFF.
BHP
LIFT 20’ 15’ 10’ 5’6.1m 4.6 m 3.1 m 1.5 m
H - Q
3HP ODP5 1/8 dia. Imp.
Example 7
COMPOSITE PERFORMANCE CURVES3500 RPM SELF-PRIMING CENTRIFUGAL
In this case, it is 3.1 BHP. The motor used is 3 HP with 1.15 service factor (3 x 1.15 = 3.45). We really have 3.45 HP to use.
Find 110 GPM at 71’ again. What is the efficiency? 66% is correct.
PAGE 12
Pump CurvesGoulds Water Technology
Pictured is a single line curve for a centrifugal pump.
Find 70 GPM at 56 ft. Since the point we need is below the head/capacity curve line, the pump will exceed our requirements.
We can have the pump meet our exact requirements by proper trimming of the impeller. This will establish a new curve for the pump. The curve will run approxi-mately parallel to the curve shown and through the point required; i.e., 70 GPM at 56 ft.
What happens if we don’t trim the impeller to meet our exact requirements? The pump will run some-where on its curve. Our head requirement is 56 ft. Follow 56 ft. horizontally to the right until you meet the curve line. Your capacity is 80 GPM. Can this instal-lation handle the additional capacity? Notice also that efficiency (EFF), brake horsepower (BHP), and net positive suction head required (NPSHR) also change, with the capacity of 80 GPM.
If we use a throttling valve on the discharge side of the pump we can regulate the capacity of the pump to 70 GPM using the standard impeller. Read vertically up from 70 GPM until you meet the curve line. The pump will make 58½ ft. Can this installation handle the extra head?
Example 8
Remember, trimming the impeller will make the pump meet your exact requirements, 70 GPM at 56 ft. (The head/capacity requirements should always be fur-nished when the pump is ordered.)
What other information is shown? Efficiency, brake horsepower, and net positive suction head required. All of these values are measured on the left hand side of the grid.
Find 70 GPM at 56 ft. again
What is the efficiency? 70.5% is correct.
What is the brake horsepower required? 1.5 BHP is correct.
What is the net positive suction head required?
NPSHR = 2.2 ft. You will have to determine the NPSHA.
NPSHA = Net Positive Suction Head available.
NPSHA has to be greater than NPSHR for the pump to work.
0GALLONS PER MINUTE
010
EFF
. %
BH
P
20 30 40 50 60 70 80 90 100 110 120
5
10
15
20
25
30
35
40
45
50
55
60
FEE
T
NP
SH
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0
10
20
30
40
50
60
70
80
H - Q
EFF.
BHP
NPSHR
Model 3756 - 2HP TEFC11/2 x 2-8 S1750 RPM - 73/4 dia. Imp.
PAGE 13
Pump CurvesGoulds Water Technology
Example 8continued
NET POSITIVE SUCTION HEAD (NPSH) AND CAVITATION
Centrifugal Pump Fundamentals
The Hydraulic Institute defines NPSH as the total suc-tion head in feet absolute, determined at the suction nozzle and corrected to datum, less the vapor pres-sure of the liquid in feet absolute. Simply stated, it is an analysis of energy conditions on the suction side of a pump to determine if the liquid will vaporize at the lowest pressure point in the pump.
The pressure which a liquid exerts on its surroundings is dependent upon its temperature. This pressure, called vapor pressure, is a unique characteristic of every fluid and increases with increasing temperature. When the vapor pressure within the fluid reaches the pressure of the surrounding medium, the fluid begins to vaporize or boil. The temperature at which this va-porization occurs will decrease as the pressure of the surrounding medium decreases.
A liquid increases greatly in volume when it vaporizes. One cubic foot of water at room temperature be-comes 1700 cu. ft. of vapor at the same temperature.
It is obvious from the above that if we are to pump a fluid effectively, we must keep it in liquid form. NPSH is simply a measure of the amount of suction head present to prevent this vaporization at the lowest pres-sure point in the pump.
NPSH Required is a function of the pump design. As the liquid passes from the pump suction to the eye of the impeller, the velocity increases and the pres-sure decreases. There are also pressure losses due to shock and turbulence as the liquid strikes the impeller. The centrifugal force of the impeller vanes further in-creases the velocity and decreases the pressure of the liquid. The NPSH Required is the positive head in feet absolute required at the pump suction to overcome these pressure drops in the pump and maintain the liquid above its vapor pressure. The NPSH Required varies with speed and capacity within any particular pump. Pump manufacturer’s curves normally provide this information.
NPSH Available is a function of the system in which the pump operates. It is the excess pressure of the liquid in feet absolute over its vapor pressure as it arrives at the pump suction. Figure 4 shows four typi-
cal suction systems with the NPSH Available formulas applicable to each. It is important to correct for the specific gravity of the liquid and to convert all terms to units of “feet absolute” in using the formulas.
In an existing system, the NPSH Available can be de-termined by a gage reading on the pump suction.
The following formula applies:
NPSHA = PB - VP ± Gr + hV
WhereGr = Gage reading at the pump suction expressed
in feet (plus if above atmospheric, minus if below atmospheric) corrected to the pump centerline.
hv= Velocity head in the suction pipe at the gage connection, expressed in feet.
Cavitation is a term used to describe the phenomenon which occurs in a pump when there is insufficient NPSH Available. The pressure of the liquid is reduced to a value equal to or below its vapor pressure and small vapor bubbles or pockets begin to form. As these vapor bubbles move along the impeller vanes to a higher pressure area, they rapidly collapse.
The collapse, or “implosion” is so rapid that it may be heard as a rumbling noise, as if you were pumping gravel. The forces during the collapse are generally high enough to cause minute pockets of fatigue fail-ure on the impeller vane surfaces. This action may be progressive, and under severe conditions can cause serious pitting damage to the impeller.
The accompanying noise is the easiest way to recog-nize cavitation. Besides impeller damage, cavitation normally results in reduced capacity due to the vapor present in the pump. Also, the head may be reduced and unstable and the power consumption may be erratic. Vibration and mechanical damage such as bearing failure can also occur as a result of operating in cavitation.
The only way to prevent the undesirable effects of cavitation is to insure that the NPSH Available in the system is greater than the NPSH Required by the pump.
PAGE 14
Pump CurvesGoulds Water Technology
NET POSITIVE SUCTION HEAD (NPSH) AND CAVITATION
PB = Barometric pressure, in feet absolute.
VP = Vapor pressure of the liquid at maximum pumping temperature, in feet absolute (see page 16).
p = Pressure on surface of liquid in closed suction tank, in feet absolute.
LS = Maximum static suction lift in feet.
LH = Minimum static suction head in feet.
hf = Friction loss in feet in suction pipe at required capacity.
Note: See Vapor Pressure Chart in Technical Manual.
4a SUCTION SUPPLY OPEN TO ATMOSPHERE– with Suction Lift
4b SUCTION SUPPLY OPEN TO ATMOSPHERE– with Suction Head
4c CLOSED SUCTION SUPPLY– with Suction Lift
4d CLOSED SUCTION SUPPLY– with Suction Head
NPSHA = PB – ( VP + LS + hf )
NPSHA = PB + LH – ( VP + hf )
NPSHA = p – ( LS + VP + hf )
NPSHA = p + LH – ( VP + hf )p
LS
CL
LS
CL
PB
LH
CL
PB
LH
CL
p
Centrifugal Pump Fundamentals
Example 8continued
PAGE 15
Pump CurvesGoulds Water Technology
Centrifugal Pump FundamentalsVAPOR PRESSURE OF WATER
5
10
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25
30
35
40 100 120 140 160 180 200 220Water Temperature ϒF
Vap
or
Pres
sure
in F
eet
of
Wat
er
60 80
15
Deduct Vapor Pressure inFeet of Water From theMaximum Allowable SuctionHead at Sea Level.
Example 8continued
PAGE 16
Pump CurvesGoulds Water Technology
Here is a centrifugal pump curve showing information that we have already covered, but in a different format.
This is a Model 3656, 1½ x 2-6 ODP.
1½ = Discharge size in inches
2 = Suction size in inches
6 = Basic diameter of the impeller in inches.
The top head/capacity curve line shows an actual impeller diameter of 515⁄16 inches.
Our requirement is 140 GPM at 95 ft. We can properly trim the impeller to meet our requirement, since the pump with the 515⁄16 inches diameter will more than meet our needs.
What happens if we install the pump and don’t trim the impeller? Our head requirement is 95 ft. Follow 95 ft. horizontally to the right until you meet the curve line. Your capacity is 157 GPM.
0 GPM
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m3/h
METERS FEET
TOTA
L D
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AM
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CAPACITY
120
10
10 20 30
40 60 80 100 120 140
40
80
NPSHR
Model 3656/375611/2 x 2-63500 RPMGroup “S”
40
160 180
160
20
30
40
50EFF.
5 15/16 dia.
5 1/8 dia.
5.5’
6’40 5060
65 70
7’ 8’
72
73
10’12’
14’
7270
65
60
50
16’18’
20’
5HP
3HP
MODELS 3656/3756 S GROUP PERFORMANCE CURVES
Example 9
If we use a throttling valve on the discharge side of the pump we can regulate the capacity of the pump to 140 GPM using the standard impeller. Read vertically up from 140 GPM until you meet the curve line. The pump will make 109 ft. Can the installation handle this extra head?
Remember, trimming the impeller to the proper diameter will make the pump meet your exact require-ments, 140 GPM at 95 ft. (The head/capacity require-ments should always be furnished when the pump is ordered.)
Consider our original requirement again: 140 GPM at 95 ft. What is the brake horsepower required? A little less than 5 HP. What is the efficiency? 71% is correct. What is the NPSHR? 13 ft. is correct.
PAGE 17
Pump CurvesGoulds Water Technology
To better understand brake horsepower as shown in these two curves, consider the following: Brake horse-power (BHP) is the actual horsepower delivered to the pump shaft. The formula for figuring brake horse-power is:
Brake Horsepower =
GPM x Feet Head x SP.GR.3960 x Pump Efficiency
Compare the two curves at 150 gallons per minute. Horsepower is given so we don’t have to calculate what it is. The grid shows an ODP motor (Open Drip Proof) which has a 1.15 service factor.
0 GPM
0
020
0
m3/h
METERS FEET
TOTA
L D
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AM
IC H
EA
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CAPACITY
120
10
10 20 30
40 60 80 100 120 140
40
80
NPSHR
Model 3656/375611/2 x 2-63500 RPMGroup “S”
40
160 180
160
20
30
40
50EFF.
5 15/16 dia.
5 1/8 dia.
5.5’
6’40 5060
6570
7’ 8’
72
73
10’12’
14’
7270
65
60
50
16’18’
20’
5HP
3HP
Example 10
5 HP x 1.15 SF =
5.75 available horsepower
The 515⁄16” diameter impeller at 150 GPM uses more than 5 HP, but does not exceed 5.75 HP.
BHP =
150 x 100 x 1.0 = 5.37 BHP 3960 x 70.5%
MODELS 3656/3756 S GROUP PERFORMANCE CURVES
PAGE 18
Pump CurvesGoulds Water Technology
Now look at the grid for TEFC motor (totally enclosed — fan cooled).
A TEFC motor has a 1.0 service factor.
5 HP x 1.0 SF =
5 available horsepower
Example 11
0 GPM
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020
0
m3/h
METERS FEET
TOTA
L D
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AM
IC H
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CAPACITY
120
10
10 20 30
40 60 80 100 120 140
40
80
Model 3656/375611/2 x 2-63500 RPMGroup “S”
40
160 180
160
20
30
40
50 EFF.
5 5/8 dia.
4 3/4 dia.
6’
4050 60 65 70
7’ 8’
72
10’
12’
14’
72
70
65
60
50
16’
18’
20’
5HP
3HP
NPSHR 5.5’
The 55⁄8” diameter impeller at 150 GPM does not exceed the 5 HP line.
BHP =
150 x 82 x 1.0 = 4.64 BHP 3960 x 67%
MODELS 3656/3756 S GROUP PERFORMANCE CURVES
PAGE 19
Pump CurvesGoulds Water Technology
Example 12
A System Head Curve is the easiest and most accu-rate way to decide which pump is best suited for an application. The factors used to create a System Head Curve are gallons per minute, friction loss data and pipe size, total head (lift or depth to water) and pres-sure desired (expressed in feet).
To be able to pick the best pump for any given job we must be given some data.
Let’s look at a 50 gpm irrigation system.
Pumping Level - 250’ at 50 gpm
Pump Set - 280’
Well Depth - 300’
Need 50 psi (115’) to operate the sprinkler heads.
Distance to 1st lateral is 1000’.
The only variable or controllable item is the pipe friction loss which varies with pipe size. We cannot change the flow, the pumping level, the pressure or the length of pipe. We will look at the difference be-tween using 1½”, 2” and 3” pipe.
We have 1000’ of offset pipe and 280’ of drop pipe for a total pipe length of 1280’. Divide the 1280 by 100, because F.L. tables show the loss per 100’ of pipe, to get a multiplier of 12.8.
We add the Total Head to the F.L. to find the TDH. Plot the Flow/TDH on any curve to show the System Head Curve for that system.
Pumping Level 250’PSI in feet 115’Total Head 365’Friction Loss + = TDH
Pipe Size GPM Friction Loss/100’ of 1½” Times 12.8 Plus 365’ Total Head 1½” 30 6.26 80 445 1½” 50 16.45 210 575 TDH 1½” 70 31.73 406 771
Pipe Size GPM Friction Loss/100’ of 2” Times 12.8 Plus 365’ Total Head 2” 30 1.81 23 388 2” 50 4.67 60 425 TDH 2” 70 8.83 113 478
Pipe Size GPM Friction Loss/100’ of 3” Times 12.8 Plus 365’ Total Head 3” 30 .26 4 369 3” 50 .66 9 374 TDH 3” 70 1.24 16 381
PUMP SYSTEM HEAD CURVE
You can see that there is a big difference in TDH due to the pipe used. The 1½” pipe would require a 15 hp pump, the 2” and 3” can use a 7.5 hp. The 2” pipe will give us 46 gpm and the 3” will yield 53 gpm. The difference of 7 gpm is 420 gph or 10,080 gpd. If you do not need the extra water use 2” and save money
on the pipe. If you need all the water you can get the 3” pipe will be much cheaper over the life of the pipe than using a larger pump. There has never been a customer who wanted less water next year than this year. Large pipe leaves room to grow the system if necessary.
PAGE 20
Pump CurvesGoulds Water Technology
Example 12continued
Plastic Pipe: Friction Loss (in feet of head) per 100 Ft.
Equivalent Number of Feet Straight Pipe for Different Fittings
GPM GPH3⁄8” ft.
½” ft.
¾” ft.
1” ft.
1¼” ft.
1½” ft.
2” ft.
2½” ft.
3” ft.
25 1,500 38.41 9.71 4.44 1.29 .54 .19
30 1,800 13.62 6.26 1.81 .75 .26
35 2,100 18.17 8.37 2.42 1.00 .35
40 2,400 23.55 10.70 3.11 1.28 .44
45 2,700 29.44 13.46 3.84 1.54 .55
50 3,000 16.45 4.67 1.93 .66
60 3,600 23.48 6.60 2.71 .93
70 4,200 31.73 8.83 3.66 1.24
80 4,800 11.43 4.67 1.58
Size of fittings, Inches ½” ¾” 1” 1¼” 1½” 2” 2½” 3” 4” 5” 6” 8” 10”90° Ell 1.5 2.0 2.7 3.5 4.3 5.5 6.5 8.0 10.0 14.0 15 20 25
45° Ell 0.8 1.0 1.3 1.7 2.0 2.5 3.0 3.8 5.0 6.3 7.1 9.4 12
Long Sweep Ell 1.0 1.4 1.7 2.3 2.7 3.5 4.2 5.2 7.0 9.0 11.0 14.0
Close Return Bend 3.6 5.0 6.0 8.3 10.0 13.0 15.0 18.0 24.0 31.0 37.0 39.0
Tee-Straight Run 1 2 2 3 3 4 5
Tee-Side Inlet or Outlet or Pitless Adapter
3.3 4.5 5.7 7.6 9.0 12.0 14.0 17.0 22.0 27.0 31.0 40.0
Ball or Globe Valve Open 17.0 22.0 27.0 36.0 43.0 55.0 67.0 82.0 110.0 140.0 160.0 220.0
Angle Valve Open 8.4 12.0 15.0 18.0 22.0 28.0 33.0 42.0 58.0 70.0 83.0 110.0
Gate Valve-Fully Open 0.4 0.5 0.6 0.8 1.0 1.2 1.4 1.7 2.3 2.9 3.5 4.5
Check Valve (Swing) 4 5 7 9 11 13 16 20 26 33 39 52 65
In Line Check Valve (Spring) or Foot Valve
4 6 8 12 14 19 23 32 43 58
PAGE 21
Pump CurvesGoulds Water Technology
0 5
20 40 60 80 10000
FLOW RATE
0
50
75
100
200
300
400
100
500150
700
TOTA
L D
YN
AM
IC H
EAD
METERS FEET
10
GPM0
10
20
30
40
50
60% EFF
175
25
125
600
200
15
55
45
35
25
15
5
m3/hr20
MODEL 55GSSIZE COMPOSITERPM 3450
225
250800
55GS15 – 5 STAGES
55GS20 – 7 STAGES
55GS30 – 9 STAGES
55GS75 – 22 STAGES
55GS100 – 29 STAGES
55GS50 – 15 STAGES
11/2” Pipe
2” Pipe
3” Pipe
Example 12continued
PAGE 22
Pump CurvesGoulds Water Technology
Example 13
The System Head Curve can be very steep when the friction loss makes up a larger part of the Total Dynam-ic Head. We see this clearly on a sewage job.
Total Lift 20’
200’ of 2” Pipe
3 Baths
2” Solids Handling Pump
As you can see from the plotted system curve it crosses 5 pump curves. You can now accurately pick the best pump for the job or tell exactly how much a certain pump will pump in a given situation. It is a good way to show customers that there is always more than one pump for every application. It also shows the wisdom of properly sizing the pipe to the flow to save horsepower and electricity.
2” PVC Pipe x 200’ long
20’ Discharge Head (Vertical Lift)
We need to pump at least 30 gpm, 2” solids.
SEWAGE SYSTEM HEAD CURVE
GPM Friction Loss at GPM
x 200 100 = +Dis. Head (Lift) = TDH
(Total Dynamic Head)20 .86 2 1.72 20’ 22’
30 1.81 2 3.62 20’ 24’
40 3.11 2 6.22 20’ 26’
50 4.67 2 9.34 20’ 29’
60 6.6 2 13.2 20’ 33’
80 11.43 2 22.86 20’ 43’
100 17.0 2 34 20’ 54’
120 24.6 2 49.2 20’ 69’
PAGE 23
Pump CurvesGoulds Water Technology
0 20 40 60 80 240 U.S. GPM0
10
20
30
40
FEET
TOTA
L D
YN
AM
IC H
EAD
0
5
10
15
METERS
FLOW RATE
SERIES: 3887BHF2" SOLIDSRPM: 3500Enclosed Impeller
100 120 140
50
0 3010 20 m3/h50
100
60
70
80
90
20
25
30
160 180 200 220
40
WS20BHF
WS15BHF
WS10BHF
WS07BHF
WS03BHF
5 FT
10 GPM
WS05BHF
This curve shows that we could use 5 different pumps on this job and pump between 33 gpm at 25’ TDH and 100 gpm at 55’ TDH.
The pumps will operate where the pump curve and system curve cross. The longer the discharge pipe the steeper the curve.
Example 13continued
Goulds is a registered trademark of Goulds Pumps, Inc. and is used under license.© 2012 Xylem Inc. CINTRO November 2007
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